Spit it out: rhoptry organelles in Plasmodium sporozoites.

Plasmodium sporozoites (SPZs), the infective stage of malaria-causing parasites, colonize the salivary glands (SGs) of Anopheles mosquitoes and are transmitted to a vertebrate host during a blood meal. SPZs are injected into the skin, travel to the liver, and invade hepatocytes to replicate to form erythrocyte-invading merozoites. In Plasmodium, as in other apicomplexan parasites, invasion of host cells requires the coordinated secretion of apical secretory organelles, the micronemes and the rhoptries. This review highlights recent advances in unraveling the function of rhoptries in Plasmodium SPZs. We discuss how genetic and imaging approaches uncovered a hitherto unsuspected role of rhoptries during invasion of the mosquito SGs and established the conserved role of a rhoptry protein complex in cell invasion in both the mosquito and mammalian hosts.